<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>javascript</title>
  <style>
    * {
      margin: 0;
      padding: 0;
      box-sizing: border-box
    }
    body {
      font-size: 14px;
      padding: 20px;
    }
    ul li {
      line-height: 30px;
    }
  </style>
</head>
<body>
  <ul>
    <li></li>
  </ul>
</body>
<script>
  var obj = {
    a: '123'
  }
   function test() {
     var title = "hello";
     function test1() {
       var title1 = 'world'
       console.log(title1)
       function test2() {
         var title2 = 'haha'
         console.log(title2)
         debugger;
       }
       test2()
     }
     test1.call(obj)
     console.log(title)
   }
   test()
</script>
</html>